What would be a game without any cheat codes helping all of us, who can't finish it without a little help, or who are  just too lazy to finish it the other way :) Trespasser doesn't make any difference in that point and this is what you can do with them:

Open or load a game. In the game press CTRL + F11. A small small blinking line should be visible on the bottom left. Now simply enter one of the cheats below. You can type in as many cheats as you want. But remember to close the small window with CTRL + F11 , when you're done:

You can also load any level you want. Simply press CTRL+SHIFT+Q+W in the level loading screen. Another screen, showing all the available level files (including the secret levels) will appear. Pick the one you want and double click on it.